This invention relates generally to an apparatus for improving the accuracy and efficacy of surgical treatments and more particularly to locating a target region to be treated and tracking the motion of the target region due to respiratory and other patient motions during the treatment.
Various different treatments may accurately track the motion of a target region in order to apply the treatment to the target region. In radiation therapy and radiosurgery, for example, a tumor may be destroyed by a beam of ionizing radiation which kills the cells in the tumor. The problem is that the tumor may move during treatment, especially due to the breathing motion of the patient. Such respiratory motion is difficult to track using external sensors, since the extent and direction of the internal breathing motion of the patient cannot be seen with traditional imaging devices. The breathing and other motion of the patient means that it is more difficult to focus the radiation on the tumor which means that the treatment may be less effective and healthy tissue may be unnecessarily damaged.
The goal of radiosurgery is to give a very high dose of radiation to the tumor only, while protecting surrounding healthy tissue as much as possible. Although radiosurgery has been applied with dramatic success to brain tumors, the extension of this technique to tumors outside the head or neck areas has eluded easy solutions. The main reason for this difficulty has been the problem of accurate target localization (i.e., accurate tracking of the motion of the target). In particular, breathing motion and other organ and patient motion make it difficult to track the target tumor with high precision. Thus, in the presence of breathing motion, for example, it is difficult to achieve the goal of providing a high dose of radiation to the tumor while protecting surrounding healthy tissue. Therefore radiosurgery is currently applied nearly exclusively to brain tumors. Conventional systems can only move the radiation beam along circular arcs in space so that irregular breathing motions cannot be easily followed since these breathing motions may not occur along the axis of the circular arcs traced by the radiation beam.
Another radiosurgery technique uses a mechanical robotic device having six degrees of freedom that targets a radiation beam as disclosed in U.S. Pat. No. 5,207,223 to Adler. The is robotic device permits the radiation treatment beam to be accurately positioned to apply the treatment beam directed to the target region. A method for neurosurgical navigation is disclosed in U.S. Pat. No. 5,769,861. This method relates to finding fixed targets, such as a brain tumor, but does not address tracking the motion of a target organ, such as lung due to breathing, with respect to the skin surface, or tracking the motion of internal abdominal organs with respect to externally visible motion. A fiducial that may be implanted into the human body so that it is detectable by an imaging system is also disclosed in which the fiducial implant is implanted into the bone or organs of the human body. This fiducial implant permits internal structures of the human body to be analyzed, but does not attempt to compensate for motion of a target organ which moves throughout the respiratory cycle. Thus, it is desirable to provide an apparatus and method for compensating for respiratory and other patient motion in radiation treatment and it is to this end that the present invention is directed.
In accordance with the invention, an apparatus and method for compensating for breathing and other motion of a patient is provided which combines internal markers placed on the target organ with one or more external sensors to accurately track the position and motion of a moving target region, such as an internal organ. In particular, the position of the internal markers, determined periodically by x-rays, may be combined with the position of the external markers/sensors. The internal markers may be imaged only periodically since an invasive technology, such as x-rays, are needed to image the internal markers. The external continuous or real-time sensor, which may be an external marker, determines external motion during treatment. Thus, the position of the target organ may be precisely determined by the position of the internal markers when the internal markers are periodically imaged and may be determined based on the external sensor data while the internal markers are not being imaged. The position and motion of the internal markers relative to the external sensors are determined so that the position of the internal markers and therefore the target organ may be accurately determined by the position of the external sensor. Thus, the position of the target organ may be accurately determined throughout the medical procedure being performed.
The internal markers may be imaged using a number of different imaging technologies, including x-rays, nuclear magnetic resonance, ultrasound and other technologies which permit markers inside of the body of the patient to be imaged. Alternatively, three dimensional ultrasound images may be used to establish the location of the internal target region in lieu of discrete fiducials. The position of the external sensor may also be determined using a number of different technologies including infrared imaging, visual imaging, magnetic localization, the measurement of respiration, and any other type of technology which permits the external markers to be imaged. In addition to using external sensors (i.e., external fiducials may not be used), it is also possible to visually image a body surface which is then correlated to the internal fiducials.
Thus, in accordance with the invention, an apparatus for performing treatment on an internal target region while measuring and in some cases compensating for breathing and other motion of the patient is provided. The apparatus comprises a first imaging device for periodically generating positional data about the internal target region and a second imaging device for continuously generating positional data about one or more external markers attached to the patient""s body. The apparatus further comprises a processor that receives the positional data about the internal target region and the external sensor readings/measurements in order to generate a correspondence between the position of the internal target region and the external marker or sensor readings and a treatment device that directs the treatment towards the position of the target region of the patient based on the positional data of the external markers or sensor readings. An apparatus for compensating for motion of a patent during treatment is also disclosed as well as a method for compensating for motion of the patient.
In accordance with another embodiment of the invention, no fiducials are attached to the target, the target is delineated in x-ray images (manually or semi-automatically), and the target""s position is subsequently matched to the position of the tumor in preoperative tomographic images. In addition, motions of the target region resulting from pulsation effects can be compensated for via a sensor by recording both pulsation data and time points of pulsation data acquisition or both pulsation and respiratory motions may be compensated for simultaneously. In addition, the deformation or squeezing of the target region may be determined and that deformation may be compensated.
In accordance with yet another aspect of the invention, a single image of the patient may be used to generate a model and then the patient is instructed to return to the position within the respiration cycle corresponding to this single point. In addition, the motion model in accordance with the invention may be continuously updated. In addition,a general model for a particular motion may be determined. In addition, the time lag between a command and the beam actually being at that position may be compensated for. Finally, respiratory motion may be distinguished from other motion.